Extension device for shotgun

ABSTRACT

The present invention relates to a shotgun accessory which can be attached to and detached from the barrel of a shotgun. A shotgun accessory formed in accordance with the invention is an accessory barrel ( 6 ), the structure of which is such that it brings about the optional combustion of the gun powder in the shotgun&#39;s barrel and accessory barrel ( 6 ).

[0001] This invention relates to a shotgun accessory which is detachable and attaches onto the barrel of a shotgun.

[0002] A shotgun is a weapon which requires gun powder and is primarily used in sport shooting and hunting. Shotguns are very versatile when used in hunting even if they are limited in their versatility by their power capacity and shooting range.

[0003] In conventional shotguns and cartridges the optimal combustion of the charge of powder cannot be attained. This is because the shotgun barrel is relatively short. When optimal combustion cannot be attained, the resulting speed and energy of the shot are not as good as they could possibly be. These matters are compounded by magnum cartridges, in which the charge of powder is delayed due to the enlarged shot load. Incomplete combustion is manifest in the shotgun barrel as powder which has been left unburned, which gives rise to excess dirt accumulation and, as is commonly known, yields a shooting range which is effectively inferior. The introduction to the market of alternative materials used in producing pellets has further compounded the problem of attaining an effective shooting range, with the specific weight of shotgun pellets made from alternative material being so much lighter than that of lead pellets.

[0004] Generally, shotguns used in hunting are equipped with a 28-36-inch barrel. Since black powder was used earlier in cartridges, shotguns were longer, but carrying them and handling them was difficult.

[0005] Attempts have been made to increase the power of shotguns by using different magnum cartridges, enlarging the pellet size, changing charge of powder and the caliber of the weapon and by making different contractions in the shotgun barrel, however none of these succeeded significantly in increasing the effective shooting range. Increases in the length of the shotgun barrel have had to be limited to preserve convenience in carrying and a broader range of use.

[0006] There are different kinds of accessories for shotguns which can be attached to and removed from the gun, but none of these accessories are designed in their structure to reach an optimal combustion of powder, nor to harness the full potential of energy available.

[0007] The present invention seeks to provide a shotgun accessory which will eliminate these disadvantages and which, when used, ensures the optimal combustion of powder and attains the optimal power potential. The object of the invention is thus to increase the distance of an effective shot significantly and still maintain a good shot pattern, which will broaden the functional possibilities of the shotgun.

[0008] These objects can be attained with a shotgun accessory formed according to the invention, the characteristics of which are set forth in the claims.

[0009] A shotgun accessory formed in accordance with the invention is an accessory barrel, the structure of which is such that the optimal combustion of the charge of powder is obtained inside the barrel and accessory barrel. When a detachable accessory barrel formed in accordance with the invention is used on a shotgun, the shotgun barrel and accessory barrel together form sufficient volume in which the charge of powder in the cartridge is able to reach the point of optimal combustion. Thus, the maximum muzzle velocity and power potential of the shot charge is attained. Thus the group of pellets are shot into the air significantly far and in a good formation, so that the shot pattern is well-formed even from a relatively great distance. With an accessory barrel formed in accordance with the invention, a significantly longer effective shooting range is attained and the versatility of the shotgun is extended. Such an accessory barrel is light and durable in structure. The accessory barrel is easy to carry with the shotgun and it is easy to attach to the shotgun barrel before shooting and correspondingly is easily removed after use.

[0010] The structure and/or volume of an accessory barrel formed in accordance with the invention can vary in different applications to shotguns depending on barrel length, cartridge shot charge and charge of powder. The accessory barrel may be as long as the shotgun barrel or longer, in which case, the length of the available barrel and the volume of the barrel and accessory barrel is doubled, or more than doubled, compared to the previous volume. The objective is to obtain optimal combustion and the maximum muzzle velocity and greatest possible power. With the lightest shot charge and the quick charges of powder, the objective can be reached with accessory barrels which have smaller volumes. The volume of the accessory barrel varies in different applications depending on the caliber of the shotgun used and the cartridge load.

[0011] When cartridge load being used is known, the accessory barrel can be chosen accordingly and thus an accessory barrel with a greater or lesser volume can be used as needed. When the accessory is attached to the shotgun barrel, the two become a single unit, the volume of which depends on the length/structure of the accessory barrel. This single unit formed by the barrel and accessory barrel is a crucial factor. The volume can even exceed the doubled volume of the shotgun barrel, in which case, the optimal combustion of the delayed charges of powder and maximum power are still attainable. With such cartridges, which contain the lightest shot loads and the quickest rate of combustion, optimal combustion can be reached with shorter accessory barrels with smaller volumes.

[0012] An accessory barrel formed in accordance with the invention advantageously comprises a special gently sloping transition cone. This transition cone reaches advantageously from the contracting part of the accessory barrel to the fixture part. With the exceptional length and gentle slope of the transition cone, placed before the actual contracting part, a minimized change to the formation of the pellets is attained before the actual contracting part, and there is a smoother release of the pellets from the barrel, so that even formation changes to individual pellets made of soft material are minimized. This creates a better trajectory course through the air and an advantageous shot pattern when shooting at long distances.

[0013] In the following application of an accessory barrel formed in accordance with the invention, the accessory barrel has a cylindrical structure. This way the contraction can be changeably either internal or external. It is also possible to use an accessory barrel which has both a transition cone and cylindrical structure.

[0014] The invention will now be described in more detail with reference to the accompanying drawing in which

[0015]FIG. 1 illustrates a certain shotgun accessory barrel formed in accordance with the invention, seen as a partial profile from the side, and

[0016]FIG. 2 illustrates an accessory barrel formed in accordance with FIG. 1, as seen from the front.

[0017] An accessory or accessory barrel frame 6 formed in accordance with the invention comprises a shotgun accessory barrel which has been produced of a material which is good enough to withstand all of the pressure and outside strain that will be put on it. At the head of the barrel there is a fully-contracted contracting part 1. Inside of the barrel, there is an especially gently sloping transition cone 2. The barrel is connected to the connecting part 7 by a brazed joint 3, or by some other corresponding means. Connecting part 7 has a tensioning relief 4 with a key for adjusting the tension. The connecting part 7 and the barrel of the shotgun have thread fillets 5 by which the accessory barrel is screwed onto the shotgun barrel as an extension. These thread fillets are in accord with the type of shotgun. The transition cone reaches from the contracting part 1 to the thread fillets of connecting part 7. Other conventional mechanisms for connecting and structures can be used in different applications of the invention.

[0018] Within the frames of the invention, solutions deviating from the ones described above can be taken into consideration. For example, connecting part 7 may be made with thread fillets in the interior and may be detachable from the accessory barrel, or it may be part of the frame 6, together forming one unit. According to the intended purpose, the contracting part may also vary. For example, the contractions may be internal. The transition cone may also have a steeper incline to minimize the volume. The accessory barrel may in some applications be a cylinder or partial cylinder.

[0019] An accessory barrel formed in accordance with the invention has been tested at the Nexplo Vihtavuori Oy Vihtavuori factory. The test was carried out by shooting different cartridges with two different shotguns, both with and without the accessory barrel. The shotguns used were the Tikka MP-2 12/76 and the Remington 1100 12/70. The table the cartridges and lists the cartridges' muzzle velocity in two discharges without the accessory barrel and then the muzzle velocity of similar cartridges in two discharges with the accessory barrel. Additionally, the table shows the average muzzle velocity without the accessory barrel and with the accessory barrel. The muzzle velocity of the cartridges was measured 5 meters away from the mouth of the barrel. The increase in muzzle velocity and the increase in power are listed as percentages next to the measurement for the accessory barrel. The following results were thus obtained: Muzzle Velocity Vo. Energy m/s avg. % increase % Gun: Remington 1100 12/70 Cartridge 70 mm Winchester 376 super XX c. 3 365 366 w/accessory barrell 407 407 407 9.3 23.4 Winchester 370 super XX c. 1 357 363 w/accessory barrel 390 415 402 10.7 22.6 Vihtavuori 354 Vismutti c. 4 351 352.5 w/accessory barrel 362 367 365 3.7 7.5 Hubertus 410 Tina n. 1 408 409 w/accessory barrel 420 418 419 2.4 5.0 Gun: Tikka MP-2 12/76 Cartridge 76 mm Winchester douple 356 X c. BB 372 364 w/accessory barrel 393 393 393 8.0 16 Gamebore 386 Tina 4.0 mm 401 393 w/accessory barrel 407 408 408 4.0 7.8 Nike c. 1 326 313 319 w/accessory barrel 347 347 347 8.8 18.3 Dap 5 c. 3 358 363 361 w/accessory barrel 376 376 376 4.2 8.5 Vihtavuori 371 Ukkometso c. 1 364 367 w/accessory barrel 387 387 387 5.4 11.2

[0020] The tests show that when the accessory barrel is used, there is an essential increase in power, in comparison to the cases where the accessory barrel is not used. It can be said that an optimal combustion of the charge of powder and the maximum power potential have been attained. This proves that when using the accessory barrel, the muzzle velocity is constant in most of the cartridges, in particular when using magnum cartridges which have delayed charges of powder. Small variations in some of the results are caused by the different properties of the cartridges, such as the quantity of powder, moisture and other matters relating to the quality of the cartridge.

[0021] The invention is not limited to the advantageous applications set forth in this patent application. The invention is versatile and its form can vary within the frames of the idea of the invention put forth in the claims. 

1. A shotgun accessory which includes a frame part (6), inside which are a transition zone (2) and a contracting part (1), a connecting part (7) which has a tension relief (4) and thread fillets (5) which enable attachment of the frame part onto the shotgun barrel, characterized in that the accessory is an accessory barrel (6) which is fastened detachable onto the shotgun barrel as an extension, which accessory barrel then formulates extra space for combustion, whereby the accessory barrel formulates an adequate total volume together with combination of shotgun barrel, so that this combination brings out the optimal combustion out of different types of shotgun cartridges inside the shotgun barrel and accessory barrel before the charge has entered the muzzle of accessory barrel (6).
 2. A shotgun accessory in accordance with claim 1 , characterized in that inside the accessory barrel (6) the transition cone (2) has gently sloping conical structure to minimize transformation of pellets in cartridges, whereby the structure/volume enables transformations of the charge both back and front part of volume of charge when the charge is advanced in the accessory barrel (6) in proportion to decreased diameter in the transition cone (2).
 3. A shotgun accessory in accordance with claim 1 characterized in that the structure of accessory barrel (6) can be varied by changing the volumes relations without decreasing the total volume, however still remaining the optimal combustion in the combination. 